Donald Trump contends that the president has vast powers concerning national security.
Photograph: Carlo Allegri/Reuters

As the Trump administration prepared to challenge a ruling against its executive order on refugees and travel from seven Muslim-majority countries, experts said the US had been brought to the brink of a full-blown constitutional crisis.

“This is an epic confrontation between the presidency and the constitution,” says Marci Hamilton, a constitutional lawyer and scholar of religion at the University of Pennsylvania.

“The moment Donald Trump suggests anyone disobey the federal court order then we will be in a constitutional crisis.”

The ruling was made on Friday night in Seattle by federal judge James Robart. On Saturday, the president attacked Robart on Twitter, calling him a “so-called judge” and saying his opinion was “ridiculous and will be overturned”.

US travel ban - a brief guide

The executive order signed by Donald Trump suspends the entire US refugee admissions system, already one of the most rigorous in the world, for 120 days. It also suspends the Syrian refugee program indefinitely, and bans entry to the US to people from seven majority-Muslim countries – Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen – for 90 days. The order has prompted a series of legal challenges, while thousands of Americans have protested outside airports and courthouses in solidarity with Muslims and migrants.

Only the fact that the Department of Justice did not file for an emergency stay on Friday night kept a constitutional crisis from developing, Hamilton said. It began the process on Saturday evening but for now, following chaos at airports last weekend, the doors to the US are once again open to vetted refugees and people with valid papers from the seven predominantly Muslim countries named in Trump’s executive order.

Robart sided with Washington state and Minnesota and declared the entire travel ban unconstitutional. Other states are also suing the government but Washington attorney general Bob Ferguson argued the widest case: that the Trump order violated the guarantee of equal protection and the first amendment’s establishment clause, infringed the constitutional right to due process and contravened the federal Immigration and Nationality Act.

Washington state and others can now be expected to go to the next level, Hamilton said, in an attempt to turn the temporary restraining order won in Seattle into a more powerful preliminary injunction and, ultimately, a permanent injunction. Fierce counter arguments from the DoJ can be expected, with potential for a trial.

“Then you are up to the level of the court of appeals and the supreme court of the United States,” Hamilton said.

That he is willing to wait before pursuing an emergency stay makes you ask what kind of ‘emergency’ is he talking about?

Marci Hamilton, constitutional lawyer

Observers were stunned by the apparent lack of legal groundwork done by the White House aides – reportedly senior counsel Steve Bannon and policy chief Steven Miller – who wrote Trump’s executive order, thereby producing a lack of clarity which contributed to chaos at airports and rulings against the administration.

Trump has argued that he must keep the nation safe from terrorists, and that the White House has huge power in matters of national security.

Protests have broken out across the country, and around the world, in the week since Trump signed the travel ban. Photograph: Molly Riley/AFP/Getty Images

A clue to the president’s vulnerability, Hamilton said, lies in the White House’s intention to seek an emergency stay – but not immediately.

“A president can override the constitution with emergency powers if there is, in fact, an emergency,” she said. “But that means a lot more than the potential that a few people might arrive over here from certain countries.

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“The 11 September 2001 terrorist attack was an emergency – the president then unilaterally shut down airports and air travel and people couldn’t get into the US for a while.

“[Trump] hasn’t produced evidence about terrorists from these countries trying to enter America. The CIA tracks terrorists all the time, there’s a system for that. And the fact that he is willing to wait … before pursuing an emergency stay again makes you ask what kind of ‘emergency’ is he talking about?”

Patrick Leahy, the ranking Democrat on the Senate judiciary committee, said in a statement on Saturday that Trump seemed intent on precipitating a constitutional crisis.

“The president’s hostility toward the rule of law is not just embarrassing, it’s dangerous,” Leahy said, calling the travel ban an “arbitrary and shameful” attempt to discriminate against Muslims.

The ban blocked nationals or non-US dual-nationals from Iran, Iraq, Syria, Yemen, Somalia, Libya and Sudan from entering the US, including permanent residents and those on valid visas, and barred all refugees for 120 days and Syrian refugees indefinitely.

The temporary restraining order (TRO) emanating from Washington will be in effect for 14 days, if a court does not grant the government’s expected request for an emergency stay. The DoJ cannot typically appeal to a court to overturn a TRO. If a TRO is turned into a preliminary injunction, it can.

The president’s hostility toward the rule of law is not just embarrassing, it’s dangerous

Patrick Leahy, Senate judiciary committee

“We are in uncharted territory,” said Paul Hughes, an immigration lawyer with Washington firm Mayer Brown.

Hughes is acting pro bono and as co-counsel with the Legal Aid Justice Center in the case of Tareq and Ammar Aziz, two Yemeni brothers who were deported from the US last weekend, having arrived at Dulles airport in Virginia. They had been en route to join their father in Michigan but were coerced, their suit claims, into relinquishing their green cards.

As a result of legal challenges, Hughes said, the brothers are due back in the US soon. The state of Virginia last week joined the brothers as plaintiffs in a suit filed against the president.

At a hearing on Friday in federal court in Alexandria, judge Leonie Brinkema said the executive order had caused chaos. She also sent a warning to Trump.

“There’s no question the president of the United States has almost – almost – unfettered power over foreign policy and border issues,” she said.